Prick each sausage about 6 times with a fork. Arrange sausages in a baking dish and cover with beer and garlic. Cover and refrigerate; marinate for about 1 hour.

Arrange onion slices in a skillet just large enough to hold all sausages. Place sausages on top and add leftover marinade to cover. Place the skillet over medium heat and gradually bring liquid to a simmer. Poach sausages until partially-cooked, about 4 to 5 minutes. Transfer sausages to a plate and pat dry if needed. Discard the onions.

Meanwhile, prepare a grill for medium-high heat cooking. Lightly brush sausages on all sides with oil and arrange on the grill. Grill until crisp and nicely browned and sausages are cooked through, about 4 to 6 minutes. Transfer sausages to a platter and let rest for 3 minutes. Serve as is or on toasted buns with condiments of your choice.

Note: We've provided special diet and nutritional information for educational purposes. But remember — we're cooks, not doctors! You should follow the advice of your health-care provider. And since product formulations change, check product labels for the most recent ingredient information. See our Terms of Service.